If the 555 is hot this is not normal, this suggests that either there is an error somewhere in the value of a component or there is a solder bridge somewhere. A good thing to would be to measure voltages at some key points. For example what voltages do you get at the collector of the trannies with and without GATE signal (which is supposed to be at least 5V). What voltage do get at the pins of the 555 ?_________________Yves

Are these measured at the collector pin of the trannies ?
If so there is definitely a problem with the input stage, the voltages that are expected are
GATE OFF
Q1 collector : close to 15V
Q2 collector : 0V
Q3 collector : 0V
GATE ON
Q1 collector : 0V
Q2 collector : close to 15V
Q3 collector : a brief (10ms) pulse to 15V and return to 0V

g.gabba wrote:

I use the YuSynth LFO for the Gate signal

when i connect the lfo with the Gate in the LED on the LFO is dark
on the Gate in is now only a +/- 1,4 V pulse - may thats the problem
Unplugged the LFO Ampl is +/-4 V
So i amplify the signal with a mixer over 3v at the Gate in

--> nothing
any idea?

OK what you say is that the input GATE level drops dramatically when it's plugged to the ADSR input. Obviously this is not normal, check the values of the input resistors (thes on the latest version are R4,R5,R6 (by the way R6 should be 22k, I must correct the schemo). Check also that D1, Q1,Q2,Q3 and Q4 are sane._________________Yves

Are these measured at the collector pin of the trannies ?
If so there is definitely a problem with the input stage, the voltages that are expected are
GATE OFF
Q1 collector : close to 15V
Q2 collector : 0V
Q3 collector : 0V
GATE ON
Q1 collector : 0V
Q2 collector : close to 15V
Q3 collector : a brief (10ms) pulse to 15V and return to 0V

Hi Yves, digging up an old thread.

My adsr isn't working I am not getting 15v on Q1 collector during GATE OFF. I am trying to trigger it with a push button. I have tried a sig gen but it didn't make any difference.
All my IC's are getting the right voltage, and I have checked my power supply polarity.
I have got others to build so I might try them to see if they work then compare the two circuits. Any help would be much appreciated.

Which version of the ADSR have you built ?
Can you simply check with a voltmeter what voltage you get on the basis of Q1 with and without pushing the button ?
It should be 0V without and something like 0.7V to 1.0V when pushing._________________Yves

Yves, i am getting some really weird errors with my circuit now. I found what may have been a short and since then the whole circuit is acting very strangly. I am getting 12v on the Vcc of my Op-amp and no voltage to any of the transistors.
I tried the other adsr I had built and that doesn't work either, the LED is premenantly on
But I will focus on the first one, I was just hoping it would work straight away so I could compare voltages and swap ic's etc...

I have built the old version, and I etched my own boards. Maybe not the best idea, but there are no shorts and the continuity is good. Most circuits I build work, its rare that 2 of the same thing don't work.
I suspected the IC's, until the circuit was giving stange voltages now I feel it could be any number of things.

I am going to replace some components and give try and get it out of its sorry state today. I will report back asap.

I tried taking pictures of the circuit but they really don't come out very well....
I swapped the 10 ohm resistors. Now I am getting an output.
The LED is lighting in responce to the settings of the front panel pots.
But the image on the scope seems to be either HIGH, gate on or LOW gate off. It doesn't seem to react to the front panel settings.

Q1
C = 0.7
B = 0
E = 0

Q2
C = 0
B = 0.7
E = 0

Q3
C = 11.2
B = 0.5
E = 0

When I push the trigger the voltages all go to '0' apart from Q3 collector, which stays at 11.2.

I think I am getting there. Will try to upload some pics with a better camera.

I few of the resistors were not working. Now I am getting a nice smooth envelopes on the scope. I haven't got a CV midi convertor yet, to test the input.
And I am still a little concerned that I am not getting correct voltages to Q1 - Q3. But I have something going now and should be able to find my own way with it.

The other circuit that had the LED permenantly ON was a dodgy transistor, but I haven't got that one working yet, but It shouldn't be too tough.
Have learnt a great deal by doing this circuit. And I have never had so many components fail on the same board before, it must have been a short!

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